Spoilers: Up to 03x15 - The Large Hadron Collision to be safe, events happen in a slightly alternate universe in the near future
Disclaimer: I don't own any part of The Big Bang Theory. I'm just borrowing their universe for my own entertainment.
Word Count: ~3300 (~13900 total)
Notes: The last part. I think this is one of the longest pieces of fanfic I've written that is actually complete. I'm horrible at finishing. :o See the end for a few final notes.

Penny goes to audition after audition and gets something about every third try. Adding the job on NCIS is definitely giving her portfolio more recognition and studios who previously ignored her at least give her more than a passing glance these days. The roles are little things like a walk-on part in a pilot episode of a show that probably won't go anywhere or a background person smiling in a commercial for some product. Little, but they're something. It happens often enough that she's flexing her time more at The Cheesecake Factory, only called when someone is sick or has an emergency and even then she knows there are others who are willing to pick up the time. Penny feels triumphant the few times she has to turn down a shift due to a shoot.

Sheldon, too, has a string of little victories. He's on the verge of finding a connection between three seemingly unrelated theorems. If he succeeds, he can publish next month and push the line proving string theory just that little bit more forward. (Secretly, he's hoping to time the publication with the next set of grant proposals to maximize the experience of victory he'll have over Leslie Winkle. He's not banking on it. Scientific discovery can't be put on a schedule, after all.)

Things are relatively normal.

Except Sheldon finds himself sparing a few thought cycles every day to think about recent events with Penny. He's torn between strengthening his resolve against physical interaction (the fact that he's sparing thought cycles on the subject is worrisome enough) and attempting to do something about it (he can't ignore the positive effects he's experienced). He's caught in an antilogy.

One night, he's sitting at his laptop staring at a blank document. He's typed up a contract 11 times. He's deleted it 11 times. Sheldon finally gets it right on the 17th try, but he doesn't bother to save the document, he only prints it. He stares at the single sheet of paper in his hands, reading it over incessantly, even though he's memorized it. He's never been this unsure about anything. At the same time, he's absolutely sure about the contract's foundation.

Sheldon walks out of his apartment and across the landing, knocking on Penny's door in his peculiar way.

The apartment door opens and Sheldon is momentarily caught off guard by the brightness of Penny's smile.

"Hey, Sheldon!" she says with a grin.

He notes, idly, that she's been much happier since her acting luck had changed. He finds the transition acceptable.

"Good evening, Penny," he finally says. He forces his fingers to relax before he creases the paper in his hands.

"What's up?" she asks when it's clear he's not saying any more.

Sheldon fiddles with the paper for a few moments before finally just handing it to her.

Penny takes the single sheet and reads it. Her smile slips and she's openly gaping.

"You can't be serious."

It's a contract. Penny has seen a few of Sheldon's contracts, even received a couple of her own, but this is the first time the contract is about something so...personal.

Sheldon has written a contract for kissing rights.

She looks at the words and then at the man who wrote them. She should be mad, but the fact that he actually looks a little nervous does something to her and she feels just a tiny bit sad.

"What's this about?"

Sheldon frowns. "I thought it was perfectly clear."

She rolls her eyes. "Why is this about?"

Sheldon's frown deepens. "That isn't a valid sentence, Penny."

She sighs and puts her hands on her hips. Her lips twitch when Sheldon grimaces as the paper crinkles in her hands.

"I know what you're asking. I want to know why."

Penny watches as Sheldon shifts from foot to foot.

"I...am relatively certain the rights laid out in the contract would be beneficial," he manages, not quite looking at her.

"For?"

"For my work, of course."

And then Penny does get mad, just a little. Mostly it's Sheldon, for obvious reasons. But there's a tiny piece of her that's mad at herself for letting this situation get out of hand.

She closes her eyes and sighs deeply. She's grateful that Sheldon isn't speaking.

When Penny opens her eyes, she stares up at him, searching for something. She sees confusion and expectation in Sheldon's gaze, but she doesn't really find anything else. She could explain it to him, how it's inappropriate to contractually bind someone to intimate relations for the sake of his work, but she's pretty sure he still won't get it. She isn't sure she could find the right words to make him see, isn't sure he was ready to want to see.

Penny shakes her head and steps back.

Sheldon cocks his head to the side in question.

"Wrong answer," she says, voice soft, and gently closes the door in his face.

She watches through the peephole as Sheldon raises his arm a half dozen times to knock on her door. Each time, she hopes he does and is glad he doesn't. When Sheldon finally retreats back to his apartment, she turns and leans on her door, staring at the contract.

Usually, Penny realizes she's made a mistake with a guy after she's spent the night with him. This is the first time she's realized it before she even thinks about inviting him in for "coffee".

Sheldon lies awake that night, thinking about the perplexing exchange he had with Penny. He isn't sure where he went wrong.

Sighing in frustration, he gets up and pulls on his robe. He won't be sleeping anytime soon.

He pads out to the kitchen, intent on warming a glass of milk, but finds himself sitting at his laptop instead. A few minutes with Google and he thinks he might have found an answer.

Sheldon sits back in his chair and stares at the ceiling for a moment. Once again, he's made too broad of an intuitive leap. He thought he'd been asking Penny to be an intellectual collaborator, contributing in a manner he thought was appropriate for her; that is, providing physical interaction. After all, Penny was the most experienced person he knew when it came to intimate relations.

It seems he'd miscalculated. Sheldon had made the assumption that all physical relations were created equal. But, based on the quick searches he'd done, kissing is different. Kissing is more complex, more intimate than coitus. Kissing is emotional.

He sits up abruptly and he suddenly realizes he's very lucky Penny hadn't punched him in the throat for that contract. He had, in effect, asked her for something deeply personal with no regard for her emotional well-being. He wonders if maybe it was pity he saw reflected in her eyes just before she shut her door.

A few nights later, Penny finally has an evening off. She'd been shooting a couple commercials downtown and hadn't really had an opportunity to hang out with the guys. In retrospect, she thinks that was probably for the better.

Ever since the incident with the contract, Penny's been waffling between outrageously mad and overwhelmingly guilty. She probably would have reacted badly at the slightest provocation from Sheldon; something like punching him in the throat and then smothering him with kisses. If that didn't confuse the guy...

She waltzes into 4A.

"Hey, guys!" she bubbles.

Howard and Raj are on the couch and Leonard is in the arm chair.

"Oh, hey, Penny," Leonard greets. "Perfect timing. You can be our fourth!"

"Fourth?" she asks, and then she realizes what night it is. "Where's Sheldon? He doesn't miss Halo night..."

"He's still at the university," Howard chimes in. "Said he had a few more things to look into."

"And you left him there?" She's still a little annoyed at the way the guys treat Sheldon sometimes.

"He said he'd call," Leonard remarks. "Raj or I will go pick him up when he's done."

Penny shakes her head and makes her way out the door.

"Where are you going? We need a fourth," Howard protests.

"Sorry, guys. You'll have to find someone else. I'm going to go get Sheldon."

"Penny, he's fine," Leonard says, trying to put her at ease. "The worst that will happen is he'll end up staying the night. He has his emergency bag."

She bites her lip and looks at the guys in turn. They don't know what's been going on between her and Sheldon, don't know that she may have triggered an emotional response from the one person she knows that tries to reject all emotional responses. They don't know how it's affected him. She doesn't know how it's affected him. She just knows it has.

"You're probably right," she says. "But I'm going to go check on him. Make sure he's not, you know, stuck."

The guys exchange looks but by the time they look back at the door, she's gone.

Sheldon is perched on the edge of his desk when Penny gets to the university. His office door is open and she stands just inside, watching him.

He has his arms crossed and he's staring at a bank of 5 whiteboards. The scene is eerily similar to one she walked in on weeks ago. She audibly sighs in relief when Sheldon moves to correct an equation, frowns a little when he doesn't acknowledge her presence.

Penny opens her mouth to speak but stops when Sheldon turns to one side. She can see his profile perfectly now and she muses, not for the first time, that Sheldon is actually quite attractive. His features are sharp, but proportional. His eyes are an intense blue. She wonders, in the back of her mind, what it would be like to have those eyes study her as closely as he's studying the whiteboards.

And it's at that moment Penny realizes she could lose it all for this man. She's always been quick to fall in love, for better or for worse. She's not sure she's in love with Sheldon, but she knows she likes him (against her better judgment, sometimes). Sheldon is the most unlikely guy for her, but somehow, someway, he's wormed his way into her life and if she's not careful, Penny's pretty sure he'll break her heart without ever realizing it. It scares the crap out of her.

Sheldon suddenly turns, then, and his eyes meet hers, pinning her in place.

"Oh," he breathes. "Hello."

Penny smiles weakly, waving a hand. "Heya, Sheldon. I just...came to check on you."

He checks his watch and his eyebrows go up slightly. "Oh, I hadn't realized so much time had passed."

They stand in awkward silence for a long moment, just staring at each other. Somehow, they manage to start speaking at the same time.

"So..."

"Penny..."

She smiles again, this time more genuinely. "You first."

He nods, then fiddles with the marker in his hands. "I wanted to apologize for the other night."

"You do?" she asks. Sheldon rarely apologizes for anything.

"Yes," he says, stepping towards her. "I did not realize until later that I had miscalculated the perceived intent of my contract to you."

"You did?"

Sheldon nods again. "I...apologize for requesting that you participate in an emotional activity without proper regard for your feelings."

"Oh, um, thanks, I guess."

They're staring at each other again. Penny is the first to look away.

"So, are you ready to go home?"

"In just a moment," Sheldon replies. He turns back to the middle whiteboard. "There's one more iteration I'd like to get through before I retire for the night. It shouldn't take long..."

He's off and rambling again. Penny listens and watches for a few moments.

But there's something different. Something...off.

Sheldon's body language is all wrong and Penny is having a hard time figuring out why.

At first, she thinks he's being sneaky and manipulative, trying to trick her into thinking he's getting stuck and, thus, in need of her particular kind of assistance. She gets a little mad at that and crosses her arms, waiting him out.

But he keeps going and she realizes that, no, this isn't Sheldon trying to get his way. This is Sheldon in the process of thinking his way into an intellectual black hole. This is Sheldon not knowing when he's perilously close to penning himself into his own mind.

That's when she realizes what's wrong with his movements. They're too frantic, too jerky. It's like the way she felt when she drank too much coffee: so wired and jittery she can't hold onto a thought long enough to know what's going on.

Before she realizes what she's doing, Penny finds herself walking into the room and grabbing hold of Sheldon's shoulders. He's still talking, still gesturing, but she pulls him down to her level and kisses him soundly.

When she pulls away, he's frozen in place, but his eyes follow her calmly.

"What was that for?"

"You were arguing yourself into a corner, sweetie."

"I hardly think that-- Oh. I see," he ponders, eyes scanning back and forth as if he's replaying something in his mind. "Yes, I suppose I was getting ahead of myself."

Penny giggles and grabs Sheldon by the sleeve.

"Come on, moonpie. It's getting late, I'm starving, and you probably haven't eaten, either."

Sheldon's stomach growls in response and he looks down in surprise, his cheeks coloring slightly.

The ride home is quiet, but not uncomfortably so. Sheldon thinks back on his observations and of the woman beside him. He wonders if maybe there isn't something to the whole emotional response aspect that he'd researched. He's fairly certain the chemical balance in his brain shifts every time he and Penny kiss. And while he's already convinced himself that the side effects have been unexpectedly positive, he ponders on the thought that the encounters have been satisfying in other ways.

Penny feels light and free as they drive home from the university. She's decided to just go with it, where Sheldon is concerned. She won't lie to herself, she's enjoying the closeness when it happens, but she's not going to dwell on it too much. She knows it will just drive her crazy. She doesn't want to over think it, the way Sheldon does, and possibly ruin a good thing. He's not ready for the full ramifications of his actions and, if she's honest with herself, she isn't, either. At least, not with Sheldon.

She called the pizza place before they left the university, so they make it to the front door right as the delivery guy pulls up. They chat amiably up to the fourth floor, Penny hoisting the pizza, and they don't even discuss any options before they go to her place to eat, leaving the guys to finish their Halo night in peace.

Days pass. Their lives move forward. Things are normal again. Well, as normal as anything can be with Sheldon Cooper in the mix.

Penny's gotten better at recognizing when he's running circles around himself and she doesn't mind so much that it's up to her to break him out of it. And if she kisses him sometimes when he doesn't strictly need it, she'll chalk it up to "misreading the signs". She doesn't feel too guilty about those mistakes. Not too much, at least.

Penny doesn't really think too deeply about it until Sheldon comes to her on his own one night.

His familiar triple knock sequence echoes through her apartment and Penny smiles slightly as she gets up from the couch and answers the door.

"Sheldon."

"Good evening, Penny. I trust you are well."

She cocks an eyebrow slightly. Does Sheldon look...nervous?

"Can't complain," she shrugs. "Do you need something?"

She watches his hands make small movements and thinks he stops just short of actually wringing them. He is nervous.

"Do you...have any tea?"

She frowns a little, not expecting that question, but turns away and heads towards the kitchen anyway. "I'll look, come on in."

He steps in and is shutting the door when she returns to him with a box of tea.

"This is all that's left. I guess I'll have to go to the sto--"

Penny idly registers the sound of the tea box hitting the ground, but at that moment, she's a little bit more than distracted. At that moment, the universe implodes.

Because one of Sheldon's hands is curled around her neck and the other is on her hip.

Because Sheldon's lips are on hers.

Because Sheldon...Sheldon...is kissing her.

On purpose.

And neither of them are stuck.

He breaks away abruptly and when her eyes flutter open, he's regarding her with an expression she's never seen before. It looks sort of like shock, surprise, fear, anxiety, and want all rolled into one. It's that last one she's not sure about. She's fairly certain he's going to bolt for the door and is surprised, yet again, when he just stands there.

"I...I..." he stammers.

It's been a few months since their first kiss, so she's stopped thinking he might be broken, but that doesn't make the sight of Sheldon flustered any less amazing. She can practically see his brain catching up to his actions.

"Fascinating," she murmurs, grinning to herself for adopting his speech.

He stills at her voice and takes a step back.

She takes a step forward but says nothing.

Sheldon swallows loudly, regaining some of his composure. "I...apologize if that was inappropriate."

She shakes her head. "It wasn't; not really. Surprised the hell out of me, but not inappropriate."

She takes another step forward and he automatically steps back, jumping when his back meets the door. He looks back at it, as if wondering where it came from. And then he speaks, his gaze just over the top of her head.

"I find that, while I engage in physical contact as little as possible, our...encounters have left me with a significant amount of data. After analyzing the information, I have concluded that our encounters have a positive effect on my productivity while eliciting an unanticipated, yet enjoyable, emotional response."

Penny tilts her head to one side and processes his words. She's pretty sure she knows what he's saying in Sheldon-ese.

"Sheldon Cooper," she drawls, the corners of her mouth twitching up. "Are you trying to tell me you ilike/i kissing me?"

He flattens himself against the door and looks to the side, making a soft, strangled noise. She realizes she's cornered him and decides to show mercy and not push him. This time.

He seems to come to some sort of conclusion and he relaxes slightly, turning to look at her fully. He steps forward and she stands her ground, looking up at him.

They stand toe to toe for what seems like hours. She's hyper aware of how close he is, can feel his body heat just that little bit. Their hands, dangling at their sides, are almost touching and she imagines she can feel an electric charge in the space between them. His eyes are dark, lids slightly hooded, and his mouth is a tiny bit open. Unconsciously, she licks her lips.

Sheldon stirs and slowly brings his hands to her face, lightly skimming the skin of her arms as he goes, making her shiver. He cups her face in his hands and her eyes droop at the sensation. His touch is warm and soft. He's not nervous now; his palms aren't clammy.

His lips press against hers softly, yet firmly, with confidence. The kiss is just that tiny, perfect bit more than chaste and it takes Penny's breath away. It's the purest, most significant kiss she's ever received.

He pulls away and rests his forehead against hers lightly.

"I trust that answers your inquiry?" His breath whispers across her skin and she smiles.

"Oh, yeah."

Sometime in the future, when Penny looks back on this day, she will pinpoint that kiss as the exact moment she falls in love with Sheldon Cooper. He will ponder for a moment and agree, proclaim it their epoch, their T-zero.

The End

Additional notes: So, this was really supposed to be about how Sheldon gets addicted to kissing Penny. I...kind of did that, but I wrote so much in Penny's POV that it actually more turned out like Penny getting addicted to kissing Sheldon. Well, that's not so bad, now is it? :D